Conveyer synchronizing control



Feb 28, 1933.

W. B. SNYDER ETAL CONVEYER SYNCHRONIZING common Filed Dec. 30, 19:51

1/ T T T v I I Inventors Wi||iam BSnyder" Dudleg E. Chambers b5 flaw wTheir Attorneg Patented Feb. 28, 1933 UNITED STATES PATENT OFFICEWILLIAM B. SNYDER AND DUDLEY E. CHAMBERS, OF- SCHENECTADY, NEW YORK,ASSIGNORS TO GENERAL ELECTRIC COMPANY, A. CORPORATION OF NEW YORKCONVEYER SYNCHRONIZING CONTROL Application filed December 30, 1931.

Our invention relates to motor control systems applied to thesynchronization of two moving elements and more particularly to thesynchronization of two conveyers, with respect to speed and with respectto the relative positions occupied by respective .points on each of saidconveyers.

One application of the principles embodied inour invention is found ina. method for mcreasing the production in a plant such as where aconveyer is utilized to transport material from one point to another anda second conveyer is arranged to receive the materialfrom the'firstconveyer and to transport it to a different part of the plant.Ordinarily, the two conveyers may be synchronized by gearing themtogether. However, for applications where it is desired to stop oneconveyer and operate the other in a reverse direction, the use of thegearing introduces many problems in repositioning the conveyers withrespect to each other. In one application of our invention it wasdesired to transport coils of wire, rod or the like on one conveyor, andhave a second conveyor arranged automatically to load itself with thecoils. Inasmuch as the coils are picked up by means of hooks on thesecond conveyer it will be seen that the two conveyers must beaccurately positioned at all times with respect to each other so thateach hook will engage itself with a coil. That is to say, the conveyersmust at all times be in positional agreement one with the other.

In carrying out our invention in one form thereof,'we provide meanspositionally re-.

sponsivc to the movement of the conveyers and arranged so that the speedof one conveyer is momentarily increased or decreased until theconveyers are brought into positional agreement and are thereafteroperated in synchronism with each other. More specifically we employmotion transmitting devices operated by eachconveyer so arranged as tocontrol by means of a motion receiving device and light sensitivedevices, the speed of one conveyer so that given points on each conveyerare brought into and maintained in correspondence with each other.

For a more detailed description of our invention, reference should nowbe had; to the Serial No. 583,900.

accompanying drawing in which we have diagrammatically illustrated ourinvention as applied to a hook conveyer and to a pin conveyer.

Referring to the drawing we have shown our invention in one form asapplied to the control of a direct current motor 10 arranged to drivethe hook conveyer 11, andto a motor 12 arranged to drive the pinconveyer 13. It Will be observed that a hook 14 is shown in engagementwith a coil 15 and illustrates the manner in which the coil 15 istransferred from the pin conveyer 13 to the hook conveyer 11. The fieldexcitation for the motor 10 is provided by a separately excited fieldwinding 1.8, while a separately excited field winding 19 and anauxiliary corrective field winding 20 serve to provide excitation forthe motor 12. There is connected respectively in series with each of therespective field windings 18,19 and 20, a corresponding field rheostat21, 22 and 23. These speed controlling rheostats are mechanicallyconnected together so that when the resistance of one rheostat is variedthe'resistance of each of the other rheostats is varied by aproportionate amount.

. In order to obtain an electrical indication of the position of theconveyer 11 while it is in operation, a motion transmitting device 25 isprovided which device is driven through a gear box 26 by the motor 10.Similarly, a second motion transmitting device 27 is driven through agear box 28 by the motor 12. A difi'erential motion receiving device 29is electrically connected to the motion transmitting devices 25 and 27so that the rotor of the poly-circuit stator windings with singlecircuit rotor windings. The differential device 29 has a poly-circuitrotor winding as well as a poly-circuit stator winding. The correctivedevice 30 is similar in construction to the difo ferential device.

The gear ratio of the gears (not shown) contained in gear boxes 26 and28 is such that the respective rotors of the transmitting de vices 25and 27 are rotated through 360 degrees for every length between adjacenthooks, and between adjacent pins of the respective conveyers. In oneinstallation this distance was equal to ten feet; therefore the motiontransmitting devices 25 and 27 were rotated through one revolution foreach ten feet of linear travel of a conveyer. The energization of theauxiliary field winding 20 is controlled by means of three lightsensitive devices 32, 33 and 34. A disk of light weight material, suchas aluminum, is mounted on an extension 36 of the shaft of thedifierential motion receiving device 29. A light source 37 is arrangedto illuminate the side of the disk opposite the light sensitive devices32, 33 and 34. v

If the speed of the pin conveyer 13 should increase and cause theposition of the pins to a leave their positions with respect to thehooks,

the motion receiving device 29 will rotate the disk 35 in a clockwisedirection so that the slot 38tprovided in the disk 35'permits light tobe directed on the light sensitive device 32. .The resultant flow ofcurrent through the light sensitive device 32 and the bias battery 32acauses a positive potential to be applied on an amplifier 39 so thatsuflicient current is produced to operate a relay 40. This relay 40 isarranged to complete an energizing circuit for a direction switch 41.The direction switch 41 upon closing completes a circuit for theauxiliary field winding 20 through a field rheostat 43 in a direction toincrease the field excitation of the motor 12 thereby slowing down themotor. Should there be considerable disagreement between 'the positionof the pins with respect to the hooks, a slot 46 provided in the disk 35permits light to be directed on the light sensitive device 34, and bymeans of an-amplifier 47 similar in construction and arrangement to theamplifier 39, a relay 48 is closed to complete an energizing circuit forthe relay 49 which operates to short circuit the field rheostat 43. Itwill thus be seen that the magnetic field produced by the winding 20 isconsiderably increased so that the motor 12 is slowed down a substantialamount. In other words, we provide for a small corrective efi'ort to beapplied to the motor 12, or for a large corrective efiort as determinedby the extent of the positional disagreement between the conveyers 11and 13.

If the speed of the conveyer 13 should decrease, the disk 35 is rotatedso that the slot 51 permits light to be directed on the light sensitivedevice 33 which device causes current to flow through an amplifyingdevice 31, thereby closing the relay 52. This relay 52 completes anenergizing circuit for a direction switch 54 so that the directionswitch applies excitation to the field winding 20 in a directionopposite to the previous case, thereby increasing the speed of the motor12. Should the disagreement between the position of conveyers 11 and 13be considerable, a slot 56 is arranged to permit light to be directed onthe light sensitive device 34 so that the amplifying device 47 againoperates to close the relay 48 which causes the relay 49 to shortcircuit the field rheostat 43 thereby further increasing the speed ofthe motor 12.

Inasmuch as it is sometimes necessary to operate the pin conveyer 13 ina reverse direction, the direction switches 59 and 60 are provided forreversing the polarit of current applied to the armature of t e motor12. The energization of the direction switches is controlled, by meansof a master switch 61. This master switch also serves to control theenergization of a pair of time delay relays 62 and 63, which in turn arerespectively arranged to complete energizing circuits for theaccelerating contactors 64 and 65 provided in the armature circuit ofthe motor 10, and fonthe accelerating contactors 67 and 68 connected inthe armature circuit of the motor 12.

With the above understanding of the elements and their organization withrespect to each other in the system, the operation of the system itselfand the manner in which the light sensitive devices 32, 33 and 34,rendered effective by the cooperation of the motion transmitting devices26 and 27 and the motion receiving device 29, function to maintain theconveyers exactly in positional agreement will be readily understoodfrom the description which follows. It will be assumed that the supplylines are suitably energized as indicated by the well understood symbolsfor direct and alternating current. In starting up the equipment themaster switch, 61 is operated to its right hand position to complete anenergizing circuit by means of conductors 66 and 66 for the operatingcoil of the line contactor 70- line contactor 67. .The closing of thedirection switch 60 serves to complete an e11- crgizing circuit for thearmature of the motor 12 so that it rotates in a clockwise direction. Apair of accelerating resistors 7 4 and are connected in series with thearmature of the motor 12 so that the motor only accelerates to a lowspeed. Inasmuch as an energizing circuit for the time closingaccelerating relay 62 is completed as soon as the master switch 61 wasoperated to its right-hand position, it will be seen that this relaywill operate to close its contact-s after a predetermined'time interval;consequently energizing circuits may be traced forthe firstaceeleratingcontactor 64 of the motor 10, and for the first accelerating contactor67 of the motor 12. By connecting both of these accelerating contactorsin parallel it will be seen that the acceleration of the motors 10 and12 occurs at the same time. A predetermined time interval after theaccelerating relay 62 closes. the accelerating relay 63 operates toclose its contacts thereby completing energizing circuits by means ofthe conductor for the second accelerating contactors 65 and 68 of therespective motors 10 and 12. The motors 10 and 12 are thereforesimultaneously accelerated to their high speed. The speed controllingrheostats 21 and 22 are adjusted until the 1110- tors 10 and 12 are 0'rating at desired speeds. At the same time the rheostat 23 is adjusted acorresponding amount so that the corrective elfort of the field winding20 is varied a corresponding amount.

Should a positional disagreement exist, however, between the positionsof the pins on the conveyer 13 and the hooks on the conveyer 11, thecorrective field 20 will be energized in a direction to immediatelycorrect this disagreement. For example, if the pin conveyer 13 is aheadof the hook conve er 11, the rotor of the mot on transmitting clevice 25will be angularly displaced with respect to the rotor of the motiontransmitting device 27 and the result will be the appearance of aninduced electromotive force on the differential motion receiving device29 thereby causing the disk 35 to be rotated in a counterclockwisedirection. The slot 51 is thereby moved so that light is directed on thelight sensitive device 33. The resulting flow of current through theamplifier 31 causes the relay 52 to close its contacts therebycompleting an energizing circuit for the direction switch 54. Thisswitch in closing connects the field winding 19 to the source of supplyso that excita tion is produced on the motor 12 in a direction to causethe motor to slow down. If the disagreement between the conveyers isquite large the disk 35 will'be rotated until the slot 56 will permitlight to reach the light sensitive device 34, so that the relay 48 willenergized, -,and as explained above this relay our invention.

will close its contacts to energize the relay 49 which operates to shortcircuit the field rheostat 43. Consequently the field excitation appliedon the motor 12 is further increased to decelera-te the motor 12. As thetwo conveyers come into positional agreement with each other thereceiving device 29 returns the disk 35 to its original position and therelays 48and 52 are successively (lee-nergized so that the motor 12resumes operation with the correct speed relation and positionalrelation with the conveyer 11 and the conveyer 13 established.

It will be understood of course that if the pin conveyer 13 lags behindthe hook conveyer 11, the slots 38 and 46 will be brought into positionto cause the energization of the direction switch 41 andthe acceleratingrelay 49. In this case, however, the corrective field winding 19 appliesexcitation to the motor 12in a direction to decrease the excitation onthe motor. Consequently the motor increases its speed until theconveyors are brought into positional agreement and thereafter functionsto maintain the conveyors in synchronism.

If it be desired to operate the pin conveyer in a reverse direction, themaster switch 61 will be operated to its left-hand position. Anenergizing circuit is thereby completed for the direction switch 60which operates to energize the armature of the motor 12 in a directionto cause it to drive the conveyer in the reverse direction. At the sametime an energizing circuit is completed for the accelerating relays 62and 63, each ofwhich time closesto, complete energizing circuits for theaccelerating 'contactors' 67 and 68.

When it is aga n desired to operate the conveyors in synchronism it isonly necessary to move the master switch to its right-hand position,inasmuch as our system will automatically operate to bring the conveyersinto positional agreement with each other.

Of course it will be understood by those skilled in the art thatconducting segments ma be substituted for the slots in the disk ancooperating conducting members used in lieu of the light sensitivedevices so that the switches 41, 49 and 54 could be directly controlled. However, such contacts may impose considerable mechanical loadon the motion receiving device 29 with detrimental effects on theaccuracy of control.

While we have shown a particular embodiment of our invention, it will beunderstood of course, that we do not wish to be limited thereto, sincemany modifications may be made and we therefore contemplate by theappended claims to cover' any modifications that fall with n the truespirit and scope of What we claim as new and desire to secure by LettersPatent of the United States is:

1. In a material conveying apparatus, the

Ill

combination of a pair of conveyers one of which is arranged to receivematerial from the other when a given point on one'conveyer is in apredetermined position with respect to a given point on the otherconveyer, of driving means for each of said conveyers, control means forone of said driving means, and means responsive to the positionaldisplacement between said conveyers for operating said control means soas to vary the speed of oneof said conveyers until said given points areagain inpositional correspondence with each other.

2. Means for maintaining two continuously moving conveyers in positionalagreement with each other, comprising a light source and a. lightsensitive device,

ment between said conve ers for varying the amount of light directed onsaid light sensitive device, and means responsive to said lightsensitive device for varying the speed-of one of said conveyers so as tobring said conveyer into positional agreement and thereafter maintainsaid conveyer in synchronism.

3. Means for maintaining two continuously moving objects in positionalagreement one with the other comprising driving means for each of saidobjects, motion transmitting devices operatively connected to each ofsaid driving means, a difierential motion receiving device responsive tosaid motion transmitting devices, light sensitive means for temporarilyvarying the speed of one of said driving means and means responsive tothe operation of said receiving device for controlling the illuminationof said light sensitive means so that the speed of one of said drivingmeans is temporarily varied until said objects are brought intopositional agree ment.

4. In combination with a pair of conveyers normally arranged to beoperated with points of one conveyer in positional agreement with pointson the other conveyer, of motors for drivin each of said conveyers, amotion transmitting device for each of said convey ers, means forgearing each of said motion transmitting devices to its respectiveconveyer so'that each of said motion-transmitting. devices is rotatedone revolution by travel of its conveyer through a predetermineddistance, a diiferential receiving device electrically connected to saidmotion transmitting devices, a light sensitive device controlled by saiddifferential device for varying the speed, of one of said driving meansto bring said points of its conveyer into positional agreement with saidpoints of the other conveyer.

5. In combination with ,at least two conveyers normally arranged to beoperated with points on each conveyer in positional agreement with eachother, of motors for driving each of said conveyers, motion transmittingand differential. means responsive to a positional disagreeranged to becontrolled by the operation of said diflerential device forvarying thespeed of one of said motors until said conveyers are brought intopositional agreement one with the other and means for deenergizing oneof said driving'm'otors and for energizing another of'said motors forreverse operation.

6. In combination with a pair of conveyers of a reversible motor fordriving one of said conveyers, a motor for driving the other of saidconveyers, position transmitting means operatively connected to each ofsaid conveyers, a differential receivingmeans electrically connected tosaid transmitting means, a light sensitive device arranged to increasethe speed of one of said motors when a positional the speed of saidmotor when a positiona disagreement 111 the other directionoccurs,

'and a third light sensitive device arranged to augment the correctiveeffort of one or the other of said light sensitive devices whenever apredetermined positional disagreement occurs so that said conveyers arequickly brought into positions approaching correspondence and arethereafter slowly brought into positional agreement.

7. In combination with a pair of conveyers arrangedto be operated withpoints of one conveyer in positional agreement with points of the otherconveyer, of driving motors for each of said conveyers, speed controlmeans for each of said motors, corrective speed control means for one ofsaid motors, means for simultaneously operating said control means andsaid corrective control means, means re sponsive to positionaldisagreement between said conveyers for operating said corrective speedcontrol means so as to increase or to decrease temporarily the speed ofone of said corrective effect of said corrective means, means responsiveto positional disa ment between said' conveyers for eontro saidcorrective means comprising a, plurahty of I light sensitive means forcontrolling the direction of app 'cation of said corrective effeet bysaid corrective means, whereby said conveyers are brought intopositional agreement and are thereafter maintained in synlO chronism.

In witness whereof, we have hereunto set our hands. WILLIAM B. SN YDER.DUDLEY E. CHAMBERS.

